Thermal dehydrobromination of beta-bromoethyl bromoaromatic compounds tends to result in the formation of excessive quantities of unwanted by-products. For example when bromoethyldibromobenzene was passed through a vertical hot tube reactor packed with glass beads at 350-500.degree. C., dehydrobromination to form ar-dibromostyrene was accomplished, but significant amounts (ca. 5%) of extraneous brominated ethylbenzene coproducts and several unknown coproducts (ca. 1%) were formed. Use of several solid catalysts in the packed column in lieu of the glass beads resulted in an increase in the quantities of these extraneous coproducts.
Levy et al U. S. Pat. No. 3,966,831 describes a process for the production of mono-, di-, and/or tribromostyrene by reacting beta-bromoethyl mono-, di-, and/or tribromobenzene at a temperature between 280 and 470.degree. C. in the presence of a free radical source and either a lower alkanol or water. As shown by Examples 6 and 7 of the patent, in reactions conducted at 360.degree. C. elimination of the the peroxide or hydroperoxide free radical source resulted in extremely low conversions to the bromostyrene (30%).